Method of and apparatus for sharpening small hand tools

ABSTRACT

A grinder for tool blades having spaced coaxial grinding and stropping wheels, the stropping wheel being of smaller diameter than the grinding wheel, and a tool carrier movable along an axis parallel to the axes of the wheels. The angle made by a blade with the stropping wheel is greater than that made with the grinding wheel to remove the burr from the blade and provide a sharp edge thereon.

United States Ptetat 1191 Williams 51 May 22, 1973 METHOD OF AND APPARATUS FOR SHARPENING SMALL HANB TOOLS Inventor: Patrick Robert Williams, M isty Hill,

Mt. Eliza, Victoria, Australia Assignee: Temtool Pty. Limited, Notting Hill,

Victoria, Australia Filed: May 6, 1971 Appl. No.: 140,909

Foreign Application Priority Data 51/122, 143 224, 84 BS, 85 BS, 74 BS, 285

[56] References Cited UNITED STATES PATENTS 1,963,394 6/1934 Yassenofi' ..51/3 3,019,562 2/1962 Price ..5 H3 2,801,497 8/ 1957 Moseley ..5 H3 1,986,520 1/1935 Oakley ..5 H143 2,248,143 7/1941 Weber ..51/3 X 1,200,420 10/1916 Green ....5 H85 BS X 1,938,521 12/1933 Fougner ..51/85 BS Primary Examiner-Donald G. Kelly Att0rneyH01man & Stern [5 7] ABSTRACT A grinder for tool blades having spaced coaxial grinding and stropping wheels, the stropping wheel being of smaller diameter than the grinding wheel, and a tool carrier movable along an axis parallel to the axes of the wheels.- The angle made by a blade with the stropping wheel is greater than that made with the grinding wheel to remove the burr from the blade and provide a sharp edge thereon.

6 Claims, 3 Drawing Figures METHOD OF AND APPARATUS FOR SHARPENING SMALL HAND TOOLS BACKGROUND OF THE INVENTION This invention relates to a method of and means for sharpening small hand tools such as carpenters chisels and plane blades but it is not limited to these specific types of tools as similar blades are used in many industries and professions.

PRIOR ART Conventional sharpening techniques used with tools of this general type, which are normally a strip of steel up to about 3 inches wide and one-half inch in thickness, have consisted of first grinding a bevelled facet on one side of the blade and then hand honing the faceted side of the blade on a fine oil stone to remove the grinding burr. Normally the bevel formed by grinding is at an angle slightly less than the angle of the honing and blades can normally be honed several times before it is again necessary to reform the bevel. The operations used in forming a satisfactory edge in the conventional way needed considerable skill to maintain the required angle across the face of the tool and unless an operator was extremely skilled a very variable degree of sharpness was obtained.

Another disadvantage of the conventional method was that the final honing operation produced a fine burr and this had to be removed by wiping the edge of the back of the blade, and this wiping reduced the sharpness of the blade. If the honing burr was not removed it tended to fold over during cutting operations thereby effectively increasing the edge thickness of the tool up to double its original thickness thereby reducing the sharpness.

US. Pat. No. 1,963,394, dated June 19, 1934 and granted to Bidor Yassenoff shows a tool grinder which includes a pair of abrasive wheels and a lapping disc all mounted coaxially and a tool carrier which can hold a tool being sharpened at a constant angle relative to the wheels and disc but which carrier must be moved from one slidable table to another in order to use the lapping disc.

US. Pat. No. 3,019,562, dated Feb. 6, 1962 and granted to R. E. Price shows a pair of coaxial grinding wheels which may be moved into contact with a workpiece and which are of different diameters so that coarse and fine grinding operations can be obtained by transverse movement of the wheels relative to the workpiece without the spacing of the axis of the wheels from the workpiece being altered.

OBJECTS AND SUMMARY OF THE INVENTION The main object of the present invention is to provide a method of and apparatus for sharpening tool blades whereby a clean keen edge is formed on the blade in a repeatable manner without any skill and in a time which is reduced relative to the conventional methods.

The invention includes applying the front facet of the blade first to a grinding wheel at a predetermined fixed angle relative thereto and then to a stropping wheel at a slightly higher angle whereby the grinding burr is removed.

Preferably, the tool is clamped on a carriage which can be moved transversely relative to the two wheels of which the grinding wheel is of a larger diameter and in which the axes of the wheels are located relative to the carriage to ensure that the difference in angle required is automatically obtained when the carriage and the attached blade is moved from the grinding wheel to the stropping wheel.

The stropping wheel may comprise a wheel of flexible material to which is applied a lapping powder in wax or other base carrier.

The invention also includes a grinder for sharpening tool blades which includes a grinding means and a stropping means, means to drive the grinding means and stropping means, a tool carrier movable transversely relative to the grinding means and the stropping means, the stropping means being located from the tool carrier by a distance greater than the grinding means whereby a blade carried by the tool carrier makes a greater angle with the stropping means than with the grinding means. Preferably, the grinder includes grinding wheels and a stropping wheel, the wheel being spaced and coaxial, means to rotate the wheels, a tool carrier adapted to receive and return a blade and movable along an axis parallel to the axes of the wheels, the diameter of the grinding wheel being greater than that of the stropping wheel whereby a blade carried by the tool carrier makes a greater angle with the stropping wheel than with the grinding wheel.

In order that the invention may be more readily understood we shall describe one specific embodiment of the apparatus and its method of operation, the description being with reference to the accompanying drawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of the grinder of the invention;

FIG. 2 is a plan view of the grinder; and

FIG. 3 is a section along line 3-3 of FIG. 2 shown in chain dash the location of the grinding wheel.

DETAILED DESCRIPTION OF THE INVENTION The tool has a casing 1 in which there is mounted a motor 2 having a shaft 3,3 extending from either side thereof with a grinding wheel 4 fitted on the shaft 3 on one side of the motor and a stropping wheel 5 fitted on the shaft 3' on the other side of the motor.

The grinding wheel is a conventional abrasive wheel of a grade suitable for the hardness of the blades to be sharpened and the strop is made of a flexible material such as leather, Corfam (Registered Trade Mark) or other similar synthetic materials.

The stropping wheel is of a smaller diameter than the grinding wheel and the reason for which will be described hereinafter.

Mounted on the casing l or a sub-frame attached thereto is a bar 6, the axis of which is parallel to the axis of the motor shaft 3,3 and on this bar there is located a movable carriage 7. As illustrated, the carriage 7 is a clamp having a lower member 8 which includes an eye 9 having a close sliding fit about the bar 6 and a lower clamp jaw 10. Attached to the jaw 10 there is an upper jaw 11 with the attachment being by screws which pass through smooth apertures in the upper jaw 11 and corresponding tapped apertures in the lower jaw. The length of the screws is sufficient to permit the thickest blade 13 for which the grinder is to be used to be located between the jaws 10, 11. If required, a lock screw 14 can be provided in the upper jaw 11 whereby the blade 13 can be positively located. If required, a guide can be provided on the lower jaw against which the blade can abut to ensure that the blade is at right angles to the bar 6.

As illustrated, upper surface of the casing is provided with a plurality of index marks 16 against which the bevelled end of the blade 13 can be located to ensure that the angle to which the bevel is to be ground is the predetermined angle and also, if required, to ensure the blade end is parallel to the axes of the wheels.

Also, if required, there can be provided on the casing or carriage an adjustable rest which helps support the blade adjacent its point of contact with the wheel to thereby limit the material removed and to aid in ensuring that the effective angle is maintained constant. There may be one such rest adjacent the grinding wheel, or one rest which can move along the grinder or two such rests, one associated with the grinding wheel and one associated with the stropping wheel.

In operation, the blade is clamped in the carriage by screws 12 and the desired length of blade protrusion is then set by location of the blade end on an index mark 16 and the locating screw 14 is tightened. The motor is started as by switch 17, and the tool is moved backwards and forwards across the grinding wheel 4 until a ground face of the required angle has been formed. At this time, the carriage 7 is slid along the bar 6 until the edge of the tool is above the stropping wheel 5. Because the stropping wheel is of slightly smaller diameter than the grinding wheel only the tip of the bevel actually contacts the strop and the lapping powder in a carrier which is carried by the stropping wheel acts upon this surface and polishes the extreme edge of the tool to a very fine degree and high polish.

At the same time, it has been found that the grinding burr formed by the grinding wheel is removed and the stropping does not form a burr. Thus, there is achieved the surprising result that the back of the blade does not have to be stropped or otherwise treated and as a result the cutting edge is not degraded.

It has been found that any surface irregularities are normally of an amplitude less than 0.040 inches and have a surface finish of the order of 0.1;!"

Microscopic examination of the edge at magnifications of up to 10,000 times indicates that the method produces an edge free of any burr greater in thickness than 0.00001 inch. It can be seen that the edge formed is thus extremely keen and can be expected to cut difficult materials cleanly and to be effective for longer periods than has previously been possible.

I claim:

1. A grinder for sharpening tool blades which includes a grinding means and a stropping means, means to drive the grinding means and stropping means, a tool carrier movable transversely relative to the grinding means and the stropping means, the stropping means being located from the tool carrier by a distance greater than the grinding means, and means mounting the tool carrier for pivotal movement about an axis parallel to its direction of transverse movement whereby a blade carried by the tool carrier makes a greater angle with the stropping means than with the grinding means.

2. A grinder for sharpening tool blades including a grinding wheel and a stropping wheel, the wheels being spaced and coaxial, means to rotate the wheels, a tool carrier for receiving and retaining a blade and movable along an axis parallel to the axes of the wheels, and means mounting the tool carrier for pivotal movement about said axis; the diameter of the grinding wheel being greater than that of the stropping wheel whereby a blade carried by the tool carrier makes a greater angle with the stropping wheel than with the grinding wheel.

3. The grinder as claimed in claim 2, wherein the means to rotate the wheels is a motor having a shaft, the wheels each being located on the shaft of the motor, one wheel being located on one side of the motor and the other wheel on the other side of the motor.

4. The grinder as claimed in claim 2 including a grinder casing, a bar parallel to the wheels axes connected to the grinder casing, the tool carrier being located on the bar, and being connected to the casing.

5. The grinder as claimed in claim 4 wherein the grinder casing is provided with at least one index mark parallel to the wheels axes, the index mark being so located that when a blade attached to the carrier is adjusted to contact the mark the blade is set so that a predetermined bevel angle will be ground thereon.

6. A method of sharpening tool blades including the steps of locating the blade in a carrier which is constrained for movement transverse to a grinding means and a stropping means and which carrier is mounted for pivotal movement about the axis of movement, moving the carrier so the blade can be contacted with the grinding means to form or reform a bevel thereon, moving the carrier transversely so the blade can be contacted with the stropping means which is spaced further from the carrier than is the grinding means, and

stropping the edge of the blade on the stropping means to remove the grinding burr from the bevel face thereby forming a sharp edge on the blade. 

1. A grinder for sharpening tool blades which includes a grinding means and a stropping means, means to drive the grinding means and stropping means, a tool carrier movable transversely relative to the grinding means and the stropping means, the stropping means being located from the tool carrier by a distance greater than the grinding means, and means mounting the tool carrier for pivotal movement about an axis parallel to its direction of transverse movement whereby a blade carried by the tool carrier makes a greater angle with the stropping means than with the grinding means.
 2. A grinder for sharpening tool blades including a grinding wheel and a stropping wheel, the wheels being spaced and coaxial, means to rotate the wheels, a tool carrier for receiving and retaining a blade and movable along an axis parallel to the axes of the wheels, and means mounting the tool carrier for pivotal movement about said axis; the diameter of the grinding wheel being greater than that of the stropping wheel whereby a blade carried by the tool carrier makes a greater angle with the stropping wheel than with the grinding wheel.
 3. The grinder as claimed in claim 2, wherein the means to rotate the wheels is a motor having a shaft, the wheels each being located on the shaft of the motor, one wheel being located on one side of the motor and the other wheel on the other side of the motor.
 4. The grinder as claimed in claim 2 including a grinder casing, a bar parallel to the wheels'' axes connected to the grinder casing, the tool carrier being located on the bar, and being connected to the casing.
 5. The grinder as claimed in claim 4 wherein the grinder casing is provided with at least one index mark parallel to the wheels'' axes, the index mark being so located that when a blade attached to the carrier is adjusted to contact the mark the blade is set so that a predetermined bevel angle will be ground thereon.
 6. A method of sharpening tool blades including the steps of locating the blade in a carrier which is constrained for movement transverse to a grinding means and a stropping means and which carrier is mounted for pivotal movement about the axis of movement, moving the carrier so the blade can be contacted with the grinding means to form or reform a bevel thereon, moving the carrier transversely so the blade can be contacted with the stropping means which is spaced further from the carrier than is the grinding means, and stropping the edge of the blade on the stropping means to remove the grinding burr from the bevel face thereby forming a sharp edge on the blade. 